diff --git a/network/main/mkstream.h b/network/main/mkstream.h
index ff224a4f5497..a478db3e8250 100644
--- a/network/main/mkstream.h
+++ b/network/main/mkstream.h
@@ -38,7 +38,7 @@ XP_ListNextEncodingType(PRBool first);
 
 /* register a mime type and a command to be executed
  */
-extern void
+extern PUBLIC void
 NET_RegisterExternalViewerCommand(char * format_in, 
 								  char * system_command, 
 								  unsigned int stream_block_size);